Old Earth: a possible science fiction anthology
Old Mars and Old Venus are anthologies of new stories set in those worlds, as they were seen in old science fiction. Martian cities far older
than any on Earth, extensive Venusian seas, etc. (I suspect some good old tropes have been left out or toned down; for example, racism.)
Old Earth would be an equivalent. Geology and geography wouldn't be as divergent from current sf norms; but much else would be different:
Humans originated on Mars, or in another solar system. (Alternatively, our species evolved from Neanderthals.)
In Manhattan, no major buildings will be constructed or demolished during the next thousand years.
England will be a world power forever. (More common from British than American authors.)
The appallingly efficient Soviet Union will be powerful for centuries to come.
The United States is the only real country in North America.
Hiroshima is afflicted with superhuman mutants.
Tobacco is harmless to humans. And the smoke causes no problems on spaceships or space stations.
Multiple personality and schizophrenia are the exact same thing.
In the 21st Century:
There are plenty of jobs for washroom attendants and elevator operators in the US.
Men are more intelligent and reasonable than women. We are in charge, as we should be. (Or women have taken over and
men are submissive.)
Tin Pan Alley music rules.
The first Black US President was at or near the bottom of the Line of Succession. He got to the White House after everyone ahead
of him died or otherwise became ineligible.
US bohemians look, talk, dress, and act like the Beats.
Flying cars took over from ground cars some time in the second half of the 20th Century.
Of course, assumptions common in today's sf won't become similarly old-fashioned. Will they?